1. Field of the Invention
This invention relates to a blend of chlorinated polyvinyl chloride with a mixture of chlorinated polyethylenes, a graft polyvinyl chloride alkyl acrylate copolymer and a mixture of a tin mercaptide with a tin carboxylate.
2. Description of the Prior Art
Polyvinyl chloride and polyvinyl chloride blended with other materials such as chlorinated polyethylenes are known and have been used for a variety of products. For examples of such blends see U.S. Pat. No. 3,006,889 Frey (1961). The problem which was overcome by the Frey invention was the difficulty of softening of the hard polyvinyl chloride. This was accomplished by blending the hard polyvinyl chloride with a softer chlorinated polyethylene. One of the problems of the softer material was that its heat distortion temperature was too low. The heat distortion problem was in part solved by the invention set forth in U.S. Pat. No. 3,299,182 Jennings et al (1967). Jennings employed a mixture of a chlorinated polyvinyl chloride having a high heat softening temperature with a small amount of a homogeneously chlorinated polyethylene.
While the prior art compositions had acceptable nonflammable characteristics and heat softening characteristics, they lacked a good balance of properties for a rigid CPVC processability, thermoformability, low smoke emission, high impact strengths and thermoformability are the properties which must be balanced. The prior art fails to teach rigid CPVC compositions which would meet low smoke requirements and which are processable into sheets and which sheets are thermoformable and which have high impact strengths. Aircraft and mass transit trim parts must be strong, resist impact, be aesthetically pleasing and generate low amounts of smoke when heated to high temperatures. The problems of smoke generation include:
(1) service personnel not being able to find the source of the problem visually, and PA1 (2) occupants of the smoke-filled plane or vehicle being unable to visually find an exit. PA1 "As indicated, polyolefins having a molecular weight of from about 20,000 to less than about 1,000,000 may be used. It has been found, however, that the molecular weight of the polyolefin has some influence on the effectiveness of the chlorinated product obtained as an impact modifier for vinyl chloride polymers. More particularly, it has been found that the polyolefins described herein having molecular weights between about 20,000 to 40,000 are most effective when chlorinated to an extent of from about 20 to 28 percent by weight of chemically combined chlorine; polyolefins having a molecular weight of from about 40,000 to 100,000 are most effective when chlorinated to an extent of from about 25 and 35 percent by weight of chemically combined chlorine; and polyolefins having molecular weights of about 100,000 or more are most effective when chlorinated to an extent of from about 30 to 38 percent by weight of chemically combined chlorine". PA1 R' is a monovalent radical selected from the group consisting of 2 to 15 carbon atom alkyl where R is hydrogen and 5 to 18 carbon atom alkyl when R is alkyl. PA1 R" is an alkylene radical containing 1 to 5 carbon atoms, and PA1 X is either the radical --O-- or a radical EQU --O(CH.sub.2 --R"--O).sub.n -- PA1 wherein n is a positive integer from 1 to 10.